1. Field of the Invention
The present invention relates to a shift register circuit, and more particularly, to a Shift register circuit having bi-directional transmission mechanism.
2. Description of the Prior Art
Along with the advantages of thin appearance, low power consumption, and low radiation, liquid crystal displays have been widely applied in various electronic products for panel displaying. The operation of a liquid crystal display is featured by varying voltage drops between opposite sides of a liquid crystal layer for twisting the angles of the liquid crystal molecules in the liquid crystal layer so that the transmittance of the liquid crystal layer can be controlled for illustrating images with the aid of the light source provided by a backlight module. In general, the liquid crystal display comprises plural pixel units, a gate driver, and a source driver. The source driver is utilized for providing a plurality of data signals to be written into the pixel units. The gate driver comprises a shift register circuit for providing a plurality of gate signals to control related writing operations of the pixel units. That is, the shift register circuit is a crucial device for providing a control of writing the data signals into the pixel units.
FIG. 1 is a schematic diagram showing a prior-art shift register circuit 100. As shown in FIG. 1, the shift register circuit 100 includes a plurality of shift register stages. For ease of explanation, the shift register circuit 100 illustrates an (N−1)th shift register stage 111, an Nth shift register stage 112, and an (N+1)th shift register stage 113. The Nth shift register stage 112 is employed to generate a gate signal SGn and a start pulse signal STn according to a first clock CK1, a second clock CK2 and a start pulse signal STn−1. The gate signal SGn is furnished to a corresponding pixel unit 103 of a pixel array 101 via a gate line GLn for providing a control of writing the data signal of the data line DLi into the pixel unit 103. The start pulse signal STn is forwarded to the (N+1)th shift register stage 113 for enabling the (N+1)th shift register stage 113 to output a gate signal SGn+1 having high voltage level.
In the operation of the shift register circuit 100, the start pulse signal of each shift register stage is forwarded only to the succeeding shift register stage so that the gate signals having high voltage level can be outputted only based on unidirectional scan sequence, which is likely to incur an occurrence of mura effect on display screen. In other words, the prior-art shift register circuit 100 having unidirectional scan operation mode is unable to provide high display quality. For that reason, with the aim of suppressing the mura effect for enhancing display quality, how to build a shift register circuit having bi-directional gate signal scan operation has become one of the most important topics nowadays.